110 THE PHYSIOLOGY OF EARTHWORMS 



exists to demonstrate the course the breakdown and synthesis take 

 (Alsterberg, 1922). 



A similar paucity of results exist for L. terrestris. An oxygen 

 debt is built up by that species under anaerobic conditions with a 

 concurrent formation of lactic acid. Upon re-admittance of oxygen 

 part of the lactic acid is oxidized, and the remainder resynthesized 

 to glycogen (Davis and Slater, 1928). Glycogen evidently acts as an 

 energy store for it is mobilized from its site in the chloragogen cells 

 and decreases in amount when earthworms are starved (van 

 Gansen, 1956). Glucose- 1 -phosphate, the first intermediate formed 

 during glycolysis, has been found but there has been no sign of 

 glucose-6-phosphate or later products in the system. However, 

 although glucose-6-phosphate has not been shown chromato- 

 graphically, de-Ley and Vercruysse (1955) obtained evidence that 

 dehydrogenase systems acting on glucose-6-phosphate, and 

 gluconate-6-phosphate are both present in Tuhifex tubifex and L. 

 terrestris suggesting that the hexose-monophosphate route is 

 extant in oligochaetes. An acid phosphatase enzyme occurs in 

 chloragogen cells but its role is not yet clear (see p, 57). 



Aerobic Metabolism 



It is also as yet too early to state that the Krebs tricarboxylic 

 acid cycle acts in the oxidative metabolism of oligochaetes, 

 although the evidence available certainly suggests that it does. 



Some of the intermediate substances in the cycle, and some of 

 the associated enzyme systems involved in the transformation occur 

 in Peloscolex velutinus and E. foetida (Petrucci, 1952, 1954). 



Pyruvic acid, the end product of glycolysis which is injected into 

 the citric acid cycle, and a-ketoglutaric acid, an intermediate 

 substance formed during the conversion of pyruvic acid, are both 

 found in fairly large quantities in the body of these two species 

 (Table 17). 



When arsenite is applied to intact worms the oxygen con- 

 sumption rate falls, indicating an interference with the oxidative 

 metabolism. At the same time the pyruvic acid content of the 

 tissues rises by ten-fold, and a-ketoglutaric acid by 14-25%. This 

 could be due to inhibition of ketoglutaric acid decarboxylase in the 

 Krebs cycle, causing a piling up of a-ketoglutaric acid. lodoacetic 

 acid, often used as an inhibitor in a stage in the glycolysis of 



